The Pentagon has cleared its throat and begun to weigh in on the literary ambitions of Assistant Secretary of Defense Richard N. Perle, saying that general counsel H. Lawrence Garrett will soon begin an inquiry into whether Perle's planned sale of rights to a yet- unwritten novel violates conflict-of-interest laws.

Spokesman Robert Sims said Garrett plans to discuss the matter with Perle as soon as Perle returns from a two-week trip that suspended bidding by publishers on his proposal.

Ten days ago, offers from publishers had exceeded $300,000. prompting Sen. Sam Nunn (D-Ga.), ranking Democrat on the Senate Armed Services Committee, to fire off a letter of protest to President Reagan. Although the proposal for the novel promises an inside look at life in the corridors of power (and emphasizes Perle's experience in those corridors), Perle said at the time that he saw no problem, since he didn't intend to write the book or to accept any money for it until after he leaves office.

There's no indication that Secretary of Defense Caspar W. Weinberger is behind the Defense counsel's decision to look into the matter. But a curious twist is that several sources told The Washington Post, when the matter first came to light, that Perle had consulted with the counsel's office in advance of offering the book to publishers. The Age of Raisin . . .

Chrysler Chairman Lee Iacocca's methods of raising renovation funds for the Statue of Liberty drew a few haughty sniffs from the National Park Service. "Gross commercialism" was the phrase directed at the franchise arrangements that allowed some companies exclusive use of the Lady Liberty logo to market their goods.

But there is, as they say, no arguing with success. So National Park Service Director William Penn Mott was in Los Angeles yesterday to endorse a project to raise money for national parks -- and to sell Raisin Bran cereal.

Balladeer John Denver will be the celebrity spokesman, and sponsor General Foods hopes the promotional campaign will raise $250,000 to improve trails in 10 national parks. The company also hopes to improve Raisin Bran's position in the $4 billion ready-to-eat cereal market.

According to a General Foods public relations spokesman, the national park campaign is "aimed at reinforcing the product's all-natural imagery, extending John Denver's brand association and stimulating supermarket and grocery store support on a local level. . . . "

Park service spokesman George Berklacy said the agency has no problem with such promotionalism "when it's done precisely according to our terms. It was an offer we couldn't refuse, and it has the potential of bringing in much more than $250,000." But is it gross commercialism? Not in the ad world, which prefers to call this sort of thing a "high-impact, cause-directed marketing campaign." Career Move . . .

This week's best objet trouve is the business card of an outfit called "Beautiful People Company." Below the title appear only the Manhattan address and telphone number of the offices, and the names of the three principals: E. Howard Hunt, Robert Kreis and Linda G. Marcus.

"Beautiful People," Hunt says, is a company set up to launch a Broadway musical of the same name, "loosely based" on the Claus von Bulow story. Author and former Watergate burglar Hunt wrote the book for the show, Kreis wrote the music, and Marcus wrote the lyrics. "We'll be having a staged reading next month for backers and producers of the show," he said.

Hunt stressed that "Beautiful People" will be a drama, not a musical comedy. "That's a bad slant lots of superficial people have latched on to," he said.

Hunt's collaborator, Kreis, was asked whether Hunt's Watergate-earned fame was a help or a hindrance in the search for backers. He said, "I would say it's a help in terms of attracting interest. Of course, it's also a help that he writes so well."From news services and staff reports